Two query programs, ntpq(ADMN) and ntpdc(ADMN), are available for use by the network administrator. The ntpq command sends queries and receives responses using NTP standard mode 6 control messages, while the ntpdc command uses NTP private mode 7 messages to send its requests. The format and content of these messages are specific to ntpdc. This command allows you to inspect a wide variety of internal counters and other state data. It also provides you with an interface to the runtime reconfiguration facility.
Both ntpdc and ntpd use seconds as the unit of time, both when reading the configuration file and when doing runtime reconfiguration. Both programs also print values in seconds. On the other hand, ntpq prints all time values in milliseconds. You must, therefore, take special care to convert values output by ntpq from milliseconds to seconds before modifying the configuration file, either manually or with ntpdc.
The ntpd daemon is designed to allow its configuration to be
modified at runtime.
Nearly everything that can be configured in the configuration
file ntp.conf may be altered using ntpdc.